mbsnrtowcs -- convert a multibyte string to a wide character string


#include <wchar.h>

size_t mbsnrtowcs(wchar_t *dest, const char **src, size_t nms, size_t len, mbstate_t *ps);


mbsnrtowcs is like mbsrtowcs, except that the number of bytes to be converted, starting at src, is limited to nms.

If dest is not a NULL pointer, mbsnrtowcs converts at most nms bytes from the multibyte string src to a wide-character string starting at dest. At most, len wide characters are written to dest. The state ps is updated.

The conversion is effectively performed by repeatedly calling:
mbrtowc(dest, *src, n, ps)
where n is some positive number, as long as this call succeeds, and then incrementing dest by one and src by the number of bytes consumed.

The conversion can stop for three reasons:

If dest is NULL, len is ignored, and the conversion proceeds as above, except that the converted wide characters are not written out to memory, and that no destination length limit exists.

In both of the above cases, if ps is a NULL pointer, a static anonymous state only known to mbsnrtowcs is used instead.

The programmer must ensure that there is room for at least len wide characters at dest.

Return Value

mbsnrtowcs returns the number of wide characters that make up the converted part of the wide character string, not including the terminating null wide character. If an invalid multibyte sequence was encountered, (size_t)(-1) is returned, and the global variable errno is set to EILSEQ.


The behavior of mbsnrtowcs depends on the LC_CTYPE category of the current locale.

Passing NULL as ps is not multi-thread safe.